Kilpatrick Pat. No. 2,892,114 is concerned with a continuous plasma generator having a shell which is an anode, a cathode, a propellant inlet tube, and a series of solenoid windings encircling the shell anode. This device utilizes a high voltage discharge, an axial rather than cusp magnetic field, and makes no provision for an acceleration system. The exhaust of this plasma generator would exhibit a wide spectrum of ion energies with an average ion exhaust velocity that is relatively low.
Patrick U.S. Pat. No. 3,209,189 is directed to a plasma generator having a shell which is connected to the positive terminal of a low voltage DC supply, a cylindrical member that is connected to the negative terminal of this low voltage supply, propellant gas inlets, and a magnet enclosing the shell. This device accelerates ions electromagnetically rather than electrostatically. The magnetic field is primarily axial, and the average ion exhaust velocities are relatively low.
Reader et al U.S. Pat. No. 3,696,646 describes an electron bombardment ion source which is to be employed as a means of propulsion in outer space. This ion surce has a shell, spaced anode sections which are interspersed with a series of magnetic pole pieces alternating in polarity, a cathode, and a propellant gas inlet. This device is essentially a multicusp ion beam source in which magnetic material serves as a segmented anode. Fe-Ni-Co magnets are usually employed in this type of device.